BOZEMAN, MONTANA — Grizzly bears have drifted into new haunts east of Jackson Hole and in the southern Wind River Range, and managers say the species now occupies all corners of the ecosystem where the population is estimated.
Interagency Grizzly Bear Study Team scientist Frank van Manen presented the latest bienniel update to maps of grizzly-occupied range at a managers meeting last week in Bozeman, Montana. When grizzly range was last assessed in 2017, the apex carnivores lived in about 94 percent of the 19,278-square-mile “demographic monitoring area” in which grizzly whereabouts are closely surveilled.
“The last iteration there was a couple of holes south and east of Jackson,” van Manen told members of the Interagency Grizzly Bear Committee’s Yellowstone Ecosystem Subcommittee who gathered Wednesday.
“Those [gaps] have basically filled in,” he said. “A large portion of the demographic monitoring area is occupied. In fact, I think we might have now reached the point where 100 percent is occupied.”
On top of the filled-out habitat within the monitoring area, grizzlies treaded into another 7,261 square miles of terrain on the fringes of their range. About 38 percent of grizzly range now spills outside the so-called DMA, where Idaho, Montana and Wyoming are required to maintain a viable population of bears.
In 2018, states were managing grizzlies and were on the brink of holding the first hunt in 44 years. Then in September, a federal judge ruled that the U.S. Fish and Wildlife Service violated the Endangered Species Act when it removed the species’ “threatened” status under the act.
Grizzly numbers within the monitoring zone have largely stagnated and were last estimated at 709, van Manen said. But, he said, the count is “very conservative” and biased low by as much as 50 percent. Outside the DMA — so in 38 percent of their range — populations are unknown.
Wyoming Game and Fish Department carnivore biologist Dan Bjornlie developed the technique used to map grizzly range, which relies on the locations of verified sightings, captures and deaths. The estimate uses 15 years of data, meaning the latest assessment covers 2004 to 2018. In the two-year span leading to the 2017 estimate, occupied range grew by 11 percent. Since then, encroachment away from the Yellowstone region’s high country core slowed, with the range jumping by 5 percent in 2017 and ’18.
Since the mid-1970s, grizzly range has stretched by an average of around 12,400 square miles per decade, van Manen said.
“That’s a pretty big chunk of land,” he said.
Typically, solo boar grizzlies are the first to repatriate old grounds where grizzlies were eradicated in the early and mid-20th century. Sows with cubs, van Manen said, can be expected to arrive five to seven years later. Last summer, Game and Fish documented grizzlies farther east than any other time in decades, near Byron in the Bighorn Basin. The wandering sow and her cubs were trapped and killed.
The most recent updates to the range map dispels Jackson Hole adages like the Gros Ventre River being a north-to-south dividing line below which grizzlies are not found. The former peninsula of unoccupied range east of Jackson filled because GPS-tracked bears have gone on walkabouts into places like the Cache Creek drainage, Bjornlie said in an interview. A motion-triggered camera that captured a grizzly in the Game Creek watershed south of town also contributed to the expansion, he said.
Wyoming’s only other formerly uninhabited parts of the DMA, located in the southern Winds, are also no longer.
“We trapped on the reservation last year, and one of those bears ranged pretty far south, filling in some of those gaps,” Bjornlie said. “Plus every year down by Lander we get a handful of sightings that slowly fill that area in.”
West of the Tetons, grizzlies are reportedly inching into new parts of Idaho. Most of the 32 grizzly conflicts the Idaho Department of Fish and Game helped resolve last year were in the Island Park and Teton Valley areas, carnivore biologist Jeremy Nicholson said at the committee meeting.
“Generally speaking, since I’ve been here, if it’s Island Park, it’s grizzly related, and Teton Valley has been black bear related,” Nicholson said. “But that’s not to say you can’t have both.”